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-   -   Ebay Diode Driver Help (http://laserpointerforums.com/f67/ebay-diode-driver-help-58443.html)

Last One Left 11-30-2010 01:29 AM

Ebay Diode Driver Help
 
Hey guys is this laser driver any good? Im thinking of using it on my red DVD diode..or two in parallel for a 445nm diode..the reason im asking about this one is because its cheap lol..but is it any good? will it really supply 500mA current? Thanks guys..

*Laser Driver*

ped 11-30-2010 07:04 AM

Re: Ebay Diode Driver Help
 
Yeah i use these their fine. They'll power a LOC no problem.

Never used them to power a 445 so i dont know about using two in parralell.

HIMNL9 11-30-2010 10:25 AM

Re: Ebay Diode Driver Help
 
Remember that those are linear drivers, not switching boost drivers ..... power supply voltage must be greater than diode forward voltage.

Also, not a good idea to use them in parallel, it can fail and burn one of them ..... for more current, you need to change the mosfet (is the component marked "DA QH"), or build one yourself .....

Last One Left 11-30-2010 10:55 AM

Re: Ebay Diode Driver Help
 
Quote:

Originally Posted by ped (Post 826165)
Yeah i use these their fine. They'll power a LOC no problem.

Never used them to power a 445 so i dont know about using two in parralell.

Ok kool, well i would use it for my red..and find out some more on the 445nm..thanks alot man..

Quote:

Originally Posted by HIMNL9 (Post 826205)
Remember that those are linear drivers, not switching boost drivers ..... power supply voltage must be greater than diode forward voltage.

Also, not a good idea to use them in parallel, it can fail and burn one of them ..... for more current, you need to change the mosfet (is the component marked "DA QH"), or build one yourself .....

Ok i think i understand..basically the driver takes voltage to work, so less voltage in the output, right?
But if i supply both of them with the proper voltage and run them in parallel why wouldn't it work? sorry for the questions, but i still need to learn :)
Also can you tell me whats an appropriate driver for the 445nm, and if possible, do you have the schematics on the on i can build? thanks alot..

HIMNL9 11-30-2010 12:09 PM

Re: Ebay Diode Driver Help
 
Quote:

Originally Posted by Last One Left (Post 826213)
But if i supply both of them with the proper voltage and run them in parallel why wouldn't it work? sorry for the questions, but i still need to learn :)
Also can you tell me whats an appropriate driver for the 445nm, and if possible, do you have the schematics on the on i can build? thanks alot..

As principle, you can use the schematic i have in my album, this is a sink driver, but basically sink and source current drivers share the same principle of work ..... also, mine was made for lab use, but the basical schematic of low powered drivers is almost the same:

http://laserpointerforums.com/member...e-driver-p.jpg

The power element (mosfet) regulate the voltage, and the sense resistor (RSense, here is the 0.1 ohm one), is used for get a voltage (call it Vsense) from the current in the load (being in serie with the load, the current is the same in the load and in the RSense, and as you probably know, a certain current flowing in a resistor cause a certain voltage at its sides, where V=R*I, basical ohm law) ..... the voltage at the sides of RSense is controlled from an operational amplifier, that compare it with a fixed and known reference voltage (call it Vref, and varying the Vref you change the output current too), and drive the mosfet in the way that Vref and Vsense are always the same ..... when current of the load decrease, Vsense decrease, so the op-amp drive the mosfet to give more voltage to the load, til the current is again the wanted one, and the same happens (in reverse) when the current increase .....

About the voltage input, yes, the driver have a minimum total dropout (basically the drop on the Rsense plus the drop on the mosfet ..... much less than the dropout of linear regulators like LM317, but still present), so if your LD have a FV of, say, 4.5V, you must use at least 5V, better if 6V, for power up the circuit ..... but at the same time, remember that in linear drivers, ALL the power not used from the load, become dissipated in heat, mainly from the mosfet ..... so, if for the same example you use 6V for your LD, and power it with 1A, the dissipated power from the mosfet is 1.4W (6V, minus 4.5V from the LD, minus 100mV from the RSense, multiplied for the current) ..... where instead if you use 12V, the circuit still work, but the mosfet need to dissipate 7.4W ..... and so on .....

Also, more the mosfet is high current made and last technology, less is its internal RdsON (the resistance of the device when it's in ON state) , and also this contribute to the power dissipation, less is the RdsON, more efficent is the mosfet, and less total dropout, and so the whole circuit (some HexFETs can reach 8 or 10 milliohm of RdsON, where old types, low current mosfets can have 300 or 400 milliohm or more)

Last One Left 11-30-2010 01:44 PM

Re: Ebay Diode Driver Help
 
Dude..thanks a million for that write up..really appreciate the time taken to do this..thanks..

So therefore lets say im using one of these drivers with a red DVD burner diode..these are the specs for the driver in question

Vcc---------Voltage Out () Max Output (1mv = 1ma)
3VDC----------2.9VDC-----------27ma
3.5VDC--------3.1VDC-----------76ma
4.0VDC--------3.3VDC----------144ma
4.5VDC--------3.5VDC----------226ma
5.0VDC--------3.6VDC----------310ma
5.5VDC--------3.6VDC----------400ma
6.0VDC--------3.75VDC---------430ma

if i use just 3.6v (three rechargeable AAA at 1.2v each) i would basically be getting a max of 74ma? what is the best voltage to supply the red with to get good results..
Also about the 445nm, i would hold back a while..i would learn with the red, first..thanks again..

HIMNL9 11-30-2010 02:07 PM

Re: Ebay Diode Driver Help
 
^ uhm, those are strange data, and apparently they are giving them in the wrong way (or, at least, without specify the internal dropout of the driver, and the FV required from the LD ..... i mean, these data depends also from the FV of the load, cannot be given without know it, usually ..... just as example, if you use it for a 1.8V IR LD, at 3VDC you must already have the possibility to fully get 400mA, if is used for a 2,4V red LD, it may require 3.5 or 4V for this, and so on ..... very strange way for give details, really .....

I'm sorry, i don't have any of them at home, for track the circuit, so probably the better way for know this, is using the "ask the seller" link on the ebay page, and ask them this in detail ..... like something similar to "i have a red laser diode with a forward voltage of xx V, can your driver provide a stable XXX mA with 3.6V input ?" ..... or similar ..... and see what they say in reply ..... usually Aixiz don't ignore questions, or at least in the past, they always replied my ones .....

Last One Left 11-30-2010 02:44 PM

Re: Ebay Diode Driver Help
 
The problem is, i pulled the diodes i have from actual burners, and im not sure what are the forward voltage required by the diode..what should i do?

HIMNL9 11-30-2010 03:48 PM

Re: Ebay Diode Driver Help
 
What DVD burner and what speed ?

Indicatively, almost all the red LDs from DVD burners that i've seen til now are from 2,3 to 2,6V FV, so you can ask for 2,5V ..... about the current, it depend from the speed of the burner, for try to guess one ..... it's a closed or open can ? ..... long or short ?

You can also find some more informations in this thread, for see if someone already posted details for your diode type .....

Last One Left 11-30-2010 03:58 PM

Re: Ebay Diode Driver Help
 
Ok its a short closed can, and i have a few of them so may be i can try one at the voltage u said..
but the question is, if the diode runs at 2.5v, how much should i input into the driver..is that the question i should ask the seller? what if i put through a higher voltage, like say 4.5v or 6v into the driver..will that destroy the diode?

fbxRdnk 11-30-2010 04:54 PM

Re: Ebay Diode Driver Help
 
I tried one of these with my 16x Sony red first build (this writeup coming shortly); 3V input gave me 2.9V out & 325mA at the diode. It wasn't very bright and didn't want to burn anything, even when properly focused. I couldn't put a good dot on a telephone pole a 1/4 mile away, but 300 feet was easy.

I also switched my power source to 4.5V in and it didn't make a difference to the output light capacity.

I switched to a flex V5 preset at 190mA and what a difference. Lights up that telephone pole @ 1/4 mile with a very nice, tight dot.

HTH

Last One Left 11-30-2010 05:24 PM

Re: Ebay Diode Driver Help
 
Quote:

Originally Posted by fbxRdnk (Post 826271)
I tried one of these with my 16x Sony red first build (this writeup coming shortly); 3V input gave me 2.9V out & 325mA at the diode. It wasn't very bright and didn't want to burn anything, even when properly focused. I couldn't put a good dot on a telephone pole a 1/4 mile away, but 300 feet was easy.

I also switched my power source to 4.5V in and it didn't make a difference to the output light capacity.

I switched to a flex V5 preset at 190mA and what a difference. Lights up that telephone pole @ 1/4 mile with a very nice, tight dot.

HTH

Ohhhh...so then ur saying that these drivers might be no good lol..but how is it possible that ur getting a 2.9volt output and 325mA current and its not working well? is the 325mA to much? what about using it with the v5 driver? does it burn better?

fbxRdnk 11-30-2010 05:45 PM

Re: Ebay Diode Driver Help
 
Quote:

Originally Posted by Last One Left (Post 826279)
Ohhhh...so then ur saying that these drivers might be no good lol..but how is it possible that ur getting a 2.9volt output and 325mA current and its not working well? is the 325mA to much? what about using it with the v5 driver? does it burn better?

I'm only stating what I found when I tested it. I still have it in my parts box for a future test. It may be possible that my VOM is bad and not giving me the right readings (it is a fluke). The 325 may be too much, but turning the pot in either direction gives a much dimmer beam.

The V5 was much brighter and it definitely burns better (190mA). When properly focused, it lights strike anywhere matches under 5 seconds without putting a black dot or line on them, they start smoking at 1 second or less. I did some very nice, clean cuts through some electrical tape as well @ 1' away from the laser.

Last One Left 11-30-2010 05:52 PM

Re: Ebay Diode Driver Help
 
Ok kool..i just dont understand whats the main difference between the flexdrive and the other one..cuz if u turn the ebay driver down to 190mA it should work exactly like ur flexdrive, but clearly it doesnt..i wonder why..
I wonder if it has to do with the pulse rate? if that makes any sense..
Did u try raising the current higher than 190mA on the v5 driver? im actually thinking of buying that now lol..

fbxRdnk 11-30-2010 06:19 PM

Re: Ebay Diode Driver Help
 
Quote:

Originally Posted by Last One Left (Post 826290)
Ok kool..i just dont understand whats the main difference between the flexdrive and the other one..cuz if u turn the ebay driver down to 190mA it should work exactly like ur flexdrive, but clearly it doesnt..i wonder why..
I wonder if it has to do with the pulse rate? if that makes any sense..
Did u try raising the current higher than 190mA on the v5 driver? im actually thinking of buying that now lol..

I may play with adjusting the ebay one again later if I get another bad dvd burner to use, or a cheap diode. I don't know why the two don't work the same, I may have gotten a bad one.

I didn't raise the current higher or mess with the preset value. It was purchased for a 405 build that ended up frying the diode. Since I wasn't out anything to test it, I put it in my red & let it shine.

Good luck with either route you take.

Last One Left 11-30-2010 06:33 PM

Re: Ebay Diode Driver Help
 
Where u from man? i have a few spare red im not using..


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